This invention relates to a digital communication station and more particularly to such a station which can handle multiple communication connections using a single communication line.
The last few years have seen a proliferation of data devices, such as word processors, computer terminals, and computers, all connected to the telephone line. It is safe to predict that in the next few years this trend will increase to the point where it will be highly desirous to have conveniently placed outlets for plugging such data devices into the telephone network. As it stands today, it is necessary to have a separate communication line run to each location where a terminal is desired much as one would do for a telephone connection.
In copending patent application of Baugh-Smith, Ser. No. 341,840, which is hereby incorporated by reference herein there is detailed an arrangement for using two time separated channels for transmitting information on a single line. The Baugh et al application discloses a multiplexed channel which can be used to provide statistically multiplexed bursty data from a number of different sources. Using the Baugh teaching, a communication set using each information field (I field) to control information to a separate destination, i.e., voice to a voice transducer and data to a data transducer has been designed to alleviate the problem of running extra communication wires to every terminal.
Using the Baugh et al approach and then realizing that signaling to the telephone station can be achieved over the multiplexed channel gives an elegant selection to a difficult problem but also leaves us with the constraint that data signaling must not be delayed waiting for the completion of voice signaling. Thus, some method must be devised to allow a data user at a telephone station to establish a connection, possibly electronically, while that station is being used to establish a separate voice connection. This constraint suggests separate S channels for each information field. Such a solution, however, reduces bandwidth and consequently affects the number of stations serviceable from a processor.
Accordingly, it is desired to establish a multi-connection telephone station using time separated information fields and multiplexed signaling capability without causing one of the information channels to be penalized because of signaling on the other channel while at the same time reducing to a minimum the amount of information contained in the S field.